Using heart preparations and isolated papillary muscles the studies are directed at elucidating the mechanisms regulating cardiac contractility and metabolism. The manner in which hormonal, adrenergic, cholinergic, ischemic and anoxic stimuli and mechanical interventions such as heart rate, preload and afterload alterations produce changes in contractility and metabolism is of particular interest. The importance of myocardial cyclic nucleotides, protein kinases and calcium is being investigated.